Chlorine hydrate, Cl.sub.2.sup.. 6H.sub.2 O, has been employed as a source of chlorine for metal-chlorine high energy density batteries, particularly those utilizing zinc and a chlorine electrode. In U.S. Pat. No. 3,713,888, the operation of such a high energy density battery and the use of chlorine hydrate to generate the chlorine during charge for the battery are described and is hereby incorporated by reference.
In prior methods of utilizing chlorine hydrate as a source of chlorine for metal-chlorine batteries, the chlorine gas is generated by contacting the hydrate with electrolyte which is at a temperature above the decomposition temperature of the hydrate. The electrolyte is returned to the battery cells, normally through passageways in carbon or graphite electrodes, to release chlorine dissolved or dispersed in it and after conversion of the chlorine to chloride ion, the chlorine hydrate is again contacted with the electrolyte resulting and the process is continued. Means are usually provided for maintaining the temperature of the chlorine hydrate below its critical point when chlorine is not needed and other means may be provided for heating the hydrate to assist in releasing chlorine from it into the electrolyte to be fed back to the battery. Also, absorber or dissolver means may be provided for finely dispersing the chlorine, as bubbles, and aiding in dissolving it in the aqueous electrolyte prior to returning to the battery. Dissolved chlorine is considered to be more reactive than bubbles of chlorine in the battery.
To control release of chlorine hydrate during discharge periods comparatively complex controls have been specified in the past. Sensors have been positioned to determine when the electrode compartment requires more chlorine and indications by these that chlorine was needed resulted in starting of a pump and opening of a set of valves to permit electrolyte to be removed from the battery, forced through the chlorine hydrate source and fed back to the electrode compartment.
Because it is intended that the high energy density battery should be utilized on motor vehicles, it is important that the apparatus for feeding chlorine should be reliable, inexpensive, of minimum size and of as few working parts as possible. Previous apparatuses, including several electronically controlled valves and motors, in addition to being more expensive than that of the present invention, included more parts which could fail. Accordingly, efforts were made by the present inventor to discover a simpler, less expensive and more trouble-free apparatus and method and such efforts resulted in the making of the present invention.